From DE 10 2012 005 206 A1 a generic fuel filter, in particular a diesel fuel filter, of an internal combustion engine and a heating sensor module are known. Here, a filter housing comprises at least one inlet for the fuel to be cleaned and at least one outlet for the clean fuel. In the interior of the filter housing, a filter element is arranged in such a manner that it separates the at least one inlet from the at least one outlet. Here, at least one heating element of the heating device is arranged in a heating chamber which is located outside the interior of the filter housing with respect to a fuel flow between the inlet and a raw side of the filter element and which is co-delimited with a module housing of the heating sensor module. This is intended to make possible building the fuel filter and also the heating sensor module as compact as possible and easily temperature-control the fuel at the same time.
For a generic fuel filter to perfectly function in the long term, the water separated in the water collection chamber has to be drained from time to time. The correct timing for this is determined by way of the water level sensor which up to now had two metal pins. However, in order to be able to completely isolate the metal pins from the fuel or from the water the metal pins were each insulated with a sealing ring. At the same time, the metal pins were coated for example with tin, silver or similar in order to be resistant to oxidation and thus creep insulation. However, the design known from the prior art in this case is not only elaborate but also expensive.